2-Cyanopyrrole was found to form (2-pyrrolylmethene)-(2-pyrrolylmethyl)im when treated with lithium aluminum hydride (LAH), followed by a mild work-up. A plausible mechanism of this reductive coupling was inferred from a series of experiments, including Al-27-NMR deuteration experiments, and the reduction of variously substituted cyanopyrroles. The mechanism, a metal chelate mediated dimerization, may be the key to understanding porphocyanine synthesis via the LAH reduction of 1,9-dicyanodipyrromethanes. (C) 1998 Elsevier Science Ltd. All rights reserved.